Action Points

The number of lung cancer deaths per 10,000 person-years that were prevented with CT-screening as compared with radiography increased according to risk quintile.

In addition, across risk quintiles, there were significant decreasing trends in the number of participants with false positive results per screening-prevented lung cancer death.

Computed tomography provided effective lung cancer screening among those with the highest risk, but was not effective among low-risk patients, researchers found.

Screening by CT-scans prevented 12 cancer deaths per 10,000 person-years among those with the highest risk of death versus 0.2 deaths among those with the lowest risk, and versus radiography (P=0.01 for trend), according to Stephanie Kovalchik, PhD, of the National Cancer Institute in Bethesda, Md., and colleagues.

Also between risk quintiles, there were decreasing numbers of false positive results per screening-prevented lung cancer death, with 1,648 false positives among those with the lowest risk and 65 among those with the highest, they wrote online in the New England Journal of Medicine.

Prior research has shown a 20% reduction in lung cancer mortality among those screened with low-dose CT versus radiography, though it has also been established that the screening should be reserved for high-risk patients. However, which patients fall into that high-risk category has not been established.

"There are a lot of things that can mimic a lung cancer on a CT," noted Reginald Munden, MD, of the University of Texas MD Anderson Cancer Center, adding that the study "significantly reduced that false positive rate by close to 40%, which is a huge factor in making lung cancer screening more effective and less expensive to patients."

The authors studied the costs and benefits of low-dose CT screening based on the prescreening risk of lung cancer death in 26,604 participants compared with 26,554 controls who underwent chest radiography as part of the National Lung Screening Trial (NLST).

Costs and benefits were based on efficacy, false positive outcomes, and number of lung cancer deaths prevented through screening, and on quintile of risk of 5-year lung cancer death.

Participants were 55 to 74 years old and had at least a 30 pack-year smoking history and were active smokers within 15 years of screening. They were randomized to receive three screenings with one of the two methods over 3 years.

Follow-up occurred over a median 5.5 years and was associated with 354 deaths in the CT group versus 442 deaths in the control group, which translated to 24.6 deaths per 10,000 person-years versus 30.9 deaths per 10,000 person-years. This showed CT was associated with a significant relative reduction of 20.4% (P=0.001).

Deaths prevented through computed tomography scanning rose "in tandem with the risk of lung cancer death," they wrote, adding that "the number of participants who would need to be screened to prevent one lung cancer death decreased significantly with an increasing risk of lung cancer death," (P<0.001).

This increase in death prevention across risk quintiles was also associated with the number of stage I tumors a patient had.

Rates of false positives for CT were high, the authors noted, though false positive rates decreased as risk of lung cancer death increased, with a rate of 97% among those in the lowest quintile versus 88% for those in the highest (P<0.001 for trend).

"The cumulative results show ... participants at highest risk for lung-cancer death accounted for a disproportionate share of the benefits of low-dose CT screening," they concluded, adding that computed tomography also decreased the rate of false positives among those at highest risk of death.

The authors suggested that "a risk-based strategy for low-dose CT screening could provide a rational, empirical framework for the inclusion of NLST-ineligible smokers at high risk for lung cancer death," adding that this strategy "would depend on the generalizability of the benefits and harms of screening that were observed in NLST participants," versus those ineligible patients at similar risk.

The study was limited by lack of consideration for potential harms of CT beyond false-positive outcomes and limited power for participants with coexisting pulmonary conditions.

The study was supported by the National Cancer Institute.

The authors declared no conflicts of interest.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

MedPageToday is a trusted and reliable source for clinical and policy coverage that directly affects the lives and practices of health care professionals.

Physicians and other healthcare professionals may also receive Continuing Medical Education (CME) and Continuing Education (CE) credits at no cost for participating in MedPage Today-hosted educational activities.